Data structures and related methods for facilitating media content processing in user-defined development projects

ABSTRACT

Data structures and related methods facilitate processing of media content for a user-defined development project. In one embodiment, a data structure comprises a chain identified field for holding identifiers for identifying chains of components that are to be employed in connection with the development project, a source identifier field for denoting a project source associated with a particular chain identifier, a project time field for denoting when, during project execution, an associated source chain is required, a source time field for denoting which portion of a source is required to support execution of the project for an associated entry in the project time field, and a dependencies field for denoting whether an associated chain is dependent on any other chain(s).

RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S.application Ser. No. 09/732,087, filed on Dec. 6, 2000, now U.S. Pat.No. 6,959,438, the disclosure of which is incorporated by referenceherein.

TECHNICAL FIELD

This invention generally relates to processing media content and, moreparticularly, to an interface and related methods for dynamicallygenerating a filter graph in a development system.

BACKGROUND

Recent advances in computing power and related technology have fosteredthe development of a new generation of powerful software applications.Gaming applications, communications applications, and multimediaapplications have particularly benefited from increased processing powerand clocking speeds. Indeed, once the province of dedicated, specialtyworkstations, many personal computing systems now have the capacity toreceive, process and render multimedia objects (e.g., audio and videocontent). While the ability to display (receive, process and render)multimedia content has been around for a while, the ability for astandard computing system to support true multimedia editingapplications is relatively new.

In an effort to satisfy this need, Microsoft Corporation introduced aninnovative development system supporting advanced user-definedmultimedia editing functions. An example of this architecture ispresented in U.S. Pat. No. 5,913,038 issued to Griffiths and commonlyowned by the assignee of the present invention, the disclosure of whichis expressly incorporated herein by reference.

In the '038 patent, Griffiths introduced the an application programinterface which, when exposed to higher-level development applications,enable a user to graphically construct a multimedia processing projectby piecing together a collection of “filters” exposed by the interface.The interface described therein is referred to as a filter graphmanager. The filter graph manager controls the data structure of thefilter graph and the way data moves through the filter graph. The filtergraph manager provides a set of component object model (COM) interfacesfor communication between a filter graph and its application. Filters ofa filter graph architecture are preferably implemented as COM objects,each implementing one or more interfaces, each of which contains apredefined set of functions, called methods. Methods are called by anapplication program or other component objects in order to communicatewith the object exposing the interface. The application program can alsocall methods or interfaces exposed by the filter graph manager object.

Filter graphs work with data representing a variety of media (ornon-media) data types, each type characterized by a data stream that isprocessed by the filter components comprising the filter graph. A filterpositioned closer to the source of the data is referred to as anupstream filter, while those further down the processing chain isreferred to as a downstream filter. For each data stream that the filterhandles it exposes at least one virtual pin (i.e., distinguished from aphysical pin such as one might find on an integrated circuit). A virtualpin can be implemented as a COM object that represents a point ofconnection for a unidirectional data stream on a filter. Input pinsrepresent inputs and accept data into the filter, while output pinsrepresent outputs and provide data to other filters. Each of the filtersinclude at least one memory buffer, wherein communication of the mediastream between filters is accomplished by a series of “copy” operationsfrom one filter to another.

As introduced in Griffiths, a filter graph has three different types offilters: source filters, transform filters, and rendering filters. Asource filter is used to load data from some source; a transform filterprocesses and passes data; and a rendering filter renders data to ahardware device or other locations (e.g., saved to a file, etc.). Anexample of a filter graph for a simplistic media rendering process ispresented with reference to FIG. 1.

FIG. 1 graphically illustrates an example filter graph for renderingmedia content. As shown, the filter graph 100 is comprised of aplurality of filters 102-114, which read, process (transform) and rendermedia content from a selected source file. As shown, the filter graphincludes each of the types of filters described above, interconnected ina linear fashion.

Products utilizing the filter graph have been well received in themarket as it has opened the door to multimedia editing using otherwisestandard computing systems. It is to be appreciated, however, that theconstruction and implementation of the filter graphs are computationallyintensive and expensive in terms of memory usage. Even the most simpleof filter graphs requires and abundance of memory to facilitate the copyoperations required to move data between filters. Thus, complex filtergraphs can become unwieldy, due in part to the linear nature ofconventional development system architecture. Moreover, it is to beappreciated that the filter graphs themselves consume memory resources,thereby compounding the issue introduced above.

Thus, what is required is a filter graph architecture which reduces thecomputational and memory resources required to support even the mostcomplex of multimedia projects. Indeed, what is required is adevelopment interface and related methods that dynamically generates afilter graph during project execution, thereby improving the perceivedperformance of the development system. Just such a solution is disclosedbelow.

SUMMARY

Data structures and related methods facilitate processing of mediacontent for a user-defined development project. In one embodiment, adata structure comprises a chain identified field for holdingidentifiers for identifying chains of components that are to be employedin connection with the development project, a source identifier fieldfor denoting a project source associated with a particular chainidentifier, a project time field for denoting when, during projectexecution, an associated source chain is required, a source time fieldfor denoting which portion of a source is required to support executionof the project for an associated entry in the project time field, and adependencies field for denoting whether an associated chain is dependenton any other chain(s).

BRIEF DESCRIPTION OF THE DRAWINGS

The same reference numbers are used throughout the figures to referencelike components and features.

FIG. 1 is a graphical representation of a conventional filter graphrepresenting a user-defined development project.

FIG. 2 is a block diagram of a computing system incorporating theteachings of the described embodiment.

FIG. 3 is a block diagram of an example software architectureincorporating the teachings of the described embodiment.

FIG. 4 is a graphical illustration of an example software-enabled matrixswitch, according to an exemplary embodiment.

FIG. 5 is a graphical representation of a data structure comprising aprogramming grid to selectively couple one or more of a scalableplurality of input pins to a scalable plurality of output pins of thematrix switch filter, in accordance with one aspect of the describedembodiment.

FIG. 6 is a graphical illustration denoting shared buffer memory betweenfilters, according to one aspect of the described embodiment.

FIG. 7 is a flow chart of an example method for generating a filtergraph, in accordance with one aspect of the described embodiment.

FIG. 8 is a flow chart of an example method for negotiating bufferrequirements between at least two adjacent filters, according to oneaspect of the described embodiment.

FIG. 9 graphically illustrates an overview of a process that takes auser-defined editing project and composites a data structure that can beused to program the matrix switch.

FIG. 10 graphically illustrates the project of FIG. 9 in greater detail.

FIG. 11 shows an exemplary matrix switch dynamically generated insupport of the project developed in FIGS. 9 and 10, according to onedescribed embodiment.

FIG. 12 illustrates a graphic representation of an exemplary datastructure that represents the project of FIG. 10, according to onedescribed embodiment.

FIGS. 13-18 graphically illustrate various states of a matrix switchprogramming grid at select points in processing the project of FIGS. 9and 10 through the matrix switch, in accordance with one describedembodiment.

FIG. 19 is a flow chart of an example method for processing mediacontent, in accordance with one described embodiment.

FIG. 20 illustrates an example project with a transition and an effect,in accordance with one described embodiment.

FIG. 21 shows an exemplary data structure in the form of a hierarchicaltree that represents the project of FIG. 20.

FIGS. 22 and 23 graphically illustrate an example matrix switchprogramming grid associated with the project of FIG. 20 at select pointsin time, according to one described embodiment.

FIG. 24 shows an example matrix switch dynamically generated andconfigured as the grid of FIGS. 22 and 23 was being processed, inaccordance with one described embodiment.

FIG. 25 shows an exemplary project in accordance with one describedembodiment.

FIG. 26 graphically illustrates an example audio editing project,according to one described embodiment.

FIG. 27 depicts an example matrix switch programming grid associatedwith the project of FIG. 26.

FIG. 28 shows an example matrix switch dynamically generated andconfigured in accordance with the programming grid of FIG. 27 to performthe project of FIG. 26, according to one described embodiment.

FIG. 29 illustrates an exemplary media processing project incorporatinganother media processing project as a composite, according to yetanother described embodiment.

FIG. 30 graphically illustrates an example data structure in the form ofa hierarchical tree structure that represents the project of FIG. 29.

FIGS. 31-37 graphically illustrate various matrix switch programminggrid states at select points in generating and configuring the matrixswitch to implement the media processing of FIG. 29.

FIG. 38 illustrates an example matrix switch suitable for use in themedia processing project of FIG. 29, according to one describedembodiment.

FIG. 38 a graphically illustrates an example data structure in the formof a hierarchical tree structure that represents a project that isuseful in understanding composites in accordance with the describedembodiments.

FIG. 39 is a flow diagram that describes steps in a method in accordancewith one described embodiment.

FIG. 40 is a flow chart of an example method for processing mediacontent, in accordance with another embodiment of the present invention.

FIG. 41 is a flow chart of an example method for dynamically generatinga filter graph during execution of a development project, according toone aspect of the present invention.

FIG. 42 illustrates an example data structure utilized to manage dynamicgraph building, according to one embodiment.

FIG. 43 graphically illustrates a filter graph during dynamic graphbuilding, according to one example implementation.

FIG. 44 graphically illustrates a filter graph with chain dependenciesduring dynamic graph building, according to one embodiment of thepresent invention.

DETAILED DESCRIPTION

Related Applications

This application is related to the following commonly-filed U.S. patentapplications, all of which are commonly assigned to Microsoft Corp., thedisclosures of which are incorporated by reference herein:

Application Ser. No. 09/731,560, entitled “An Interface and RelatedMethods for Reducing Source Accesses in a Development System”, namingDaniel J. Miller and Eric H. Rudolph as inventors;

Application Ser. No. 09/731,490, entitled “A System and Related Methodsfor Reducing Source Filter Invocation in a Development Project”, namingDaniel J. Miller and Eric H. Rudolph as inventors;

Application Ser. No. 09/732,452, entitled “A System and Related Methodsfor Reducing Memory Requirements of a Media Processing System”, namingDaniel J. Miller and Eric H. Rudolph as inventors;

Application Ser. No. 09/731,529, entitled “A System and Related Methodsfor Reducing the Instances of Source Files in a Filter Graph”, namingDaniel J. Miller and Eric H. Rudolph as inventors;

Application Ser. No. 09/732,090, entitled “A System and Related Methodsfor Processing Audio Content in a Filter Graph”, naming Daniel J. Millerand Eric H. Rudolph as inventors;

Application Ser. No. 09/732,085, entitled “A System and Methods forGenerating an Managing Filter Strings in a Filter Graph”, naming DanielJ. Miller and Eric H. Rudolph as inventors;

Application Ser. No. 09/731,491, entitled “Methods and Systems forProcessing Media Content”, naming Daniel J. Miller and Eric H. Rudolphas inventors;

Application Ser. No. 09/731,563, entitled “Systems for Managing MultipleInputs and Methods and Systems for Processing Media Content”, namingDaniel J. Miller and Eric H. Rudolph as inventors;

Application Ser. No. 09/731,892, entitled “Methods and Systems forImplementing Dynamic Properties on Objects that Support Only StaticProperties”, naming Daniel J. Miller and David Maymudes as inventors;

Application Ser. No. 09/732,089, entitled “Methods and Systems forEfficiently Processing Compressed and Uncompressed Media Content”,naming Daniel J. Miller and Eric H. Rudolph as inventors;

Application Ser. No. 09/731,581, entitled “Methods and Systems forEffecting Video Transitions Represented By Bitmaps”, naming Daniel J.Miller and David Maymudes as inventors;

Application Ser. No. 09/732,372, entitled “Methods and Systems forMixing Digital Audio Signals”, naming Eric H. Rudolph as inventor; and

Application Ser. No. 09/732,086, entitled “Methods and Systems forProcessing Multi-media Editing Projects”, naming Eric H. Rudolph asinventor.

Various described embodiments concern an application program interfaceassociated with a development system. According to one exampleimplementation, the interface is exposed to a media processingapplication to enable a user to dynamically generate complex mediaprocessing tasks, e.g., editing projects. In the discussion herein,aspects of the invention are developed within the general context ofcomputer-executable instructions, such as program modules, beingexecuted by one or more conventional computers. Generally, programmodules include routines, programs, objects, components, datastructures, etc. that perform particular tasks or implement particularabstract data types. Moreover, those skilled in the art will appreciatethat the invention may be practiced with other computer systemconfigurations, including hand-held devices, personal digitalassistants, multiprocessor systems, microprocessor-based or programmableconsumer electronics, network PCs, minicomputers, mainframe computers,and the like. In a distributed computer environment, program modules maybe located in both local and remote memory storage devices. It is noted,however, that modification to the architecture and methods describedherein may well be made without deviating from spirit and scope of thepresent invention. Moreover, although developed within the context of amedia processing system paradigm, those skilled in the art willappreciate, from the discussion to follow, that the application programinterface may well be applied to other development systemimplementations. Thus, the media processing system described below isbut one illustrative implementation of a broader inventive concept.

Example System Architecture

FIG. 2 illustrates an example of a suitable computing environment 200 onwhich the system and related methods for processing media content may beimplemented.

It is to be appreciated that computing environment 200 is only oneexample of a suitable computing environment and is not intended tosuggest any limitation as to the scope of use or functionality of themedia processing system. Neither should the computing environment 200 beinterpreted as having any dependency or requirement relating to any oneor combination of components illustrated in the exemplary computingenvironment 200.

The media processing system is operational with numerous other generalpurpose or special purpose computing system environments orconfigurations. Examples of well known computing systems, environments,and/or configurations that may be suitable for use with the mediaprocessing system include, but are not limited to, personal computers,server computers, thin clients, thick clients, hand-held or laptopdevices, multiprocessor systems, microprocessor-based systems, set topboxes, programmable consumer electronics, network PCs, minicomputers,mainframe computers, distributed computing environments that include anyof the above systems or devices, and the like.

In certain implementations, the system and related methods forprocessing media content may well be described in the general context ofcomputer-executable instructions, such as program modules, beingexecuted by a computer. Generally, program modules include routines,programs, objects, components, data structures, etc. that performparticular tasks or implement particular abstract data types. The mediaprocessing system may also be practiced in distributed computingenvironments where tasks are performed by remote processing devices thatare linked through a communications network. In a distributed computingenvironment, program modules may be located in both local and remotecomputer storage media including memory storage devices.

In accordance with the illustrated example embodiment of FIG. 2computing system 200 is shown comprising one or more processors orprocessing units 202, a system memory 204, and a bus 206 that couplesvarious system components including the system memory 204 to theprocessor 202.

Bus 206 is intended to represent one or more of any of several types ofbus structures, including a memory bus or memory controller, aperipheral bus, an accelerated graphics port, and a processor or localbus using any of a variety of bus architectures. By way of example, andnot limitation, such architectures include Industry StandardArchitecture (ISA) bus, Micro Channel Architecture (MCA) bus, EnhancedISA (EISA) bus, Video Electronics Standards Association (VESA) localbus, and Peripheral Component Interconnects (PCI) buss also known asMezzanine bus.

Computer 200 typically includes a variety of computer readable media.Such media may be any available media that is locally and/or remotelyaccessible by computer 200, and it includes both volatile andnon-volatile media, removable and non-removable media.

In FIG. 2, the system memory 204 includes computer readable media in theform of volatile, such as random access memory (RAM) 210, and/ornon-volatile memory, such as read only memory (ROM) 208. A basicinput/output system (BIOS) 212, containing the basic routines that helpto transfer information between elements within computer 200, such asduring start-up, is stored in ROM 208. RAM 210 typically contains dataand/or program modules that are immediately accessible to and/orpresently be operated on by processing unit(s) 202.

Computer 200 may further include other removable/non-removable,volatile/non-volatile computer storage media. By way of example only,FIG. 2 illustrates a hard disk drive 228 for reading from and writing toa non-removable, non-volatile magnetic media (not shown and typicallycalled a “hard drive”), a magnetic disk drive 230 for reading from andwriting to a removable, non-volatile magnetic disk 232 (e.g., a “floppydisk”), and an optical disk drive 234 for reading from or writing to aremovable, non-volatile optical disk 236 such as a CD-ROM, DVD-ROM orother optical media. The hard disk drive 228, magnetic disk drive 230,and optical disk drive 234 are each connected to bus 206 by one or moreinterfaces 226.

The drives and their associated computer-readable media providenonvolatile storage of computer readable instructions, data structures,program modules, and other data for computer 200. Although the exemplaryenvironment described herein employs a hard disk 228, a removablemagnetic disk 232 and a removable optical disk 236, it should beappreciated by those skilled in the art that other types of computerreadable media which can store data that is accessible by a computer,such as magnetic cassettes, flash memory cards, digital video disks,random access memories (RAMs), read only memories (ROM), and the like,may also be used in the exemplary operating environment.

A number of program modules may be stored on the hard disk 228, magneticdisk 232, optical disk 236, ROM 208, or RAM 210, including, by way ofexample, and not limitation, an operating system 214, one or moreapplication programs 216 (e.g., multimedia application program 224),other program modules 218, and program data 220. In accordance with theillustrated example embodiment of FIG. 2, operating system 214 includesan application program interface embodied as a render engine 222. Aswill be developed more fully below, render engine 222 is exposed tohigher-level applications (e.g., 216) to automatically assemble filtergraphs in support of user-defined development projects, e.g., mediaprocessing projects. Unlike conventional media processing systems,however, render engine 222 utilizes a scalable, dynamicallyreconfigurable matrix switch to reduce filter graph complexity, therebyreducing the computational and memory resources required to complete adevelopment project. Various aspects of the innovative media processingsystem represented by a computer 200 implementing the innovative renderengine 222 will be developed further, below.

Continuing with FIG. 2, a user may enter commands and information intocomputer 200 through input devices such as keyboard 238 and pointingdevice 240 (such as a “mouse”). Other input devices may include aaudio/video input device(s) 253, a microphone, joystick, game pad,satellite dish, serial port, scanner, or the like (not shown). These andother input devices are connected to the processing unit(s) 202 throughinput interface(s) 242 that is coupled to bus 206, but may be connectedby other interface and bus structures, such as a parallel port, gameport, or a universal serial bus (USB).

A monitor 256 or other type of display device is also connected to bus206 via an interface, such as a video adapter 244. In addition to themonitor, personal computers typically include other peripheral outputdevices (not shown), such as speakers and printers, which may beconnected through output peripheral interface 246.

Computer 200 may operate in a networked environment using logicalconnections to one or more remote computers, such as a remote computer250. Remote computer 250 may include many or all of the elements andfeatures described herein relative to computer 200 including, forexample, render engine 222 and one or more development applications 216utilizing the resources of render engine 222.

As shown in FIG. 2. computing system 200 is communicatively coupled toremote devices (e.g., remote computer 250) through a local area network(LAN) 251 and a general wide area network (WAN) 252. Such networkingenvironments are commonplace in offices, enterprise-wide computernetworks, intranets, and the Internet.

When used in a LAN networking environment, the computer 200 is connectedto LAN 251 through a suitable network interface or adapter 248. Whenused in a WAN networking environment, the computer 200 typicallyincludes a modem 254 or other means for establishing communications overthe WAN 252. The modem 254, which may be internal or external, may beconnected to the system bus 206 via the user input interface 242, orother appropriate mechanism.

In a networked environment, program modules depicted relative to thepersonal computer 200, or portions thereof, may be stored in a remotememory storage device. By way of example, and not limitation, FIG. 2illustrates remote application programs 216 as residing on a memorydevice of remote computer 250. It will be appreciated that the networkconnections shown and described are exemplary and other means ofestablishing a communications link between the computers may be used.

Turning next to FIG. 3, a block diagram of an example development systemarchitecture is presented, in accordance with one embodiment of thepresent invention. In accordance with the illustrated example embodimentof FIG. 3, development system 300 is shown comprising one or moreapplication program(s) 216 coupled to render engine 222 via anappropriate communications interface 302. As used herein, applicationprogram(s) 216 are intended to represent any of a wide variety ofapplications which may benefit from use of render engine 222 such as,for example a media processing application 224.

The communications interface 302 is intended to represent any of anumber of alternate interfaces used by operating systems to exposeapplication program interface(s) to applications. According to oneexample implementation, interface 302 is a component object model (COM)interface, as used by operating systems offered by MicrosoftCorporation. As introduced above, COM interface 302 provides a means bywhich the features of the render engine 222, to be described more fullybelow, are exposed to an application program 216.

In accordance with the illustrated example implementation of FIG. 3,render engine 222 is presented comprising source filter(s) 304A-N,transform filter(s) 306A-N and render filter 310, coupled togetherutilizing virtual pins to facilitate a user-defined media processingproject. According to one implementation, the filters of system 300 aresimilar to the filters exposed in conventional media processing systems.According to one implementation, however, filters are not coupled viasuch interface pins. Rather, alternate implementations are envisionedwherein individual filters (implemented as objects) make calls to otherobjects, under the control of the render engine 222, for the desiredinput. Unlike conventional systems, however, render engine 222 exposes ascalable, dynamically reconfigurable matrix switch filter 308,automatically generated and dynamically configured by render engine 222to reduce the computational and memory resource requirements oftenassociated with development projects. As introduced above, the pins(input and/or output) are application interface(s) designed tocommunicatively couple other objects (e.g., filters).

In accordance with the example implementation of a media processingsystem, an application communicates with an instance of render engine222 when the application 216 wants to process streaming media content.Render engine 222 selectively invokes and controls an instance of filtergraph manager (not shown) to automatically create a filter graph byinvoking the appropriate filters (e.g., source, transform andrendering). As introduced above, the communication of media contentbetween filters is achieved by either (1) coupling virtual output pinsof one filter to the virtual input pins of requesting filter; or (2) byscheduling object calls between appropriate filters to communicate therequested information. As shown, source filter 304 receives streamingdata from the invoking application or an external source (not shown). Itis to be appreciated that the streaming data can be obtained from a fileon a disk, a network, a satellite feed, an Internet server, a videocassette recorder, or other source of media content. As introducedabove, transform filter(s) 306 take the media content and processes itin some manner, before passing it along to render filter 310. As usedherein, transform filter(s) 306 are intended to represent a wide varietyof processing methods or applications that can be performed on mediacontent. In this regard, transform filter(s) 306 may well include asplitter, a decoder, a sizing filter, a transition filter, an effectsfilter, and the like. The function of each of these filters is describedmore fully in the Griffiths application, introduced above, and generallyincorporated herein by reference. The transition filter, as used herein,is utilized by render engine 222 to transition the rendered output froma first source to a second source. The effect filter is selectivelyinvoked to introduce a particular effect (e.g., fade, wipe, audiodistortion, etc.) to a media stream.

In accordance with one aspect of the embodiment, to be described morefully below, matrix switch filter 308 selectively passes media contentfrom one or more of a scalable plurality of input(s) to a scalableplurality of output(s). Moreover, matrix switch 308 also supportsimplementation of a cascaded architecture utilizing feedback paths,i.e., wherein transform filters 306B, 306C, etc. coupled to the outputof matrix switch 308 are dynamically coupled to one or more of thescalable plurality of matrix switch input(s). An example of thiscascaded filter graph architecture is introduced in FIG. 3, and furtherexplained in example implementations, below.

Typically, media processed through source, transform and matrix switchfilters are ultimately passed to render filter 310, which provides thenecessary interface to a hardware device, or other location that acceptsthe renderer output format, such as a memory or disk file, or arendering device.

FIG. 4 is a graphical illustration of an example software-enabled matrixswitch 308, according to one example embodiment of the presentinvention. As shown, the matrix switch 308 is comprised of a scalableplurality of input(s) 402 and a scalable plurality of output(s) 404,wherein any one or more of the input(s) 402 may be iteratively coupledto any one or more of the output(s) 404, based on the content of thematrix switch programming grid 406, automatically generated by renderengine 222. According to an alternate implementation introduced above,switch matrix 308 is programmed by render engine 222 to dynamicallygenerate object calls to communicate media content between filters. Inaddition, according to one implementation, matrix switch 308 includes aplurality of input/output (I/O) buffers 408, as well as means formaintaining source, or media time 410 and/or timeline, or project time412. It is to be appreciated, however, that in alternate implementationsmatrix switch 308 does not maintain both source and project times,relying on an upstream filter to convert between these times. As will bedeveloped more fully below, matrix switch 308 dynamically couples one ormore of the scalable plurality of inputs 402 to one or more of thescalable plurality of outputs 404 based, at least in part, on the mediatime 410 and/or the project time 412 and the content of matrix switchprogramming grid 406. In this regard, matrix switch 308 may becharacterized as time-aware, supporting such advanced editing featuresas searching/seeking to a particular point (e.g., media time) in themedia content, facilitating an innovative buffering process utilizingI/O buffers 408 to facilitate look-ahead processing of media content,and the like. Thus, it will be appreciated given the discussion tofollow that introduction of the matrix switch 308 provides a user withan editing flexibility that was heretofore unavailable in a personalcomputer-based media processing system.

As introduced above, the inputs 402 and outputs 404 of matrix switch 308are interfaces which facilitate the time-sensitive routing of data(e.g., media content) in accordance with a user-defined developmentproject. Matrix switch 308 has a scalable plurality of inputs 402 andoutputs 404, meaning that the number of inputs 402 and outputs 404 areindividually generated to satisfy a given editing project. Insofar aseach of the inputs/outputs (I/O) has an associated transfer buffer(preferably shared with an adjacent filter) to communicate mediacontent, the scalability of the input/output serves to reduce theoverall buffer memory consumed by an editing project. According to oneimplementation, output 1 is generally reserved as a primary output,e.g., coupled to a rendering filter (not shown).

According to one implementation, for each input 402 and output 404,matrix switch 308 attempts to be the allocator, or manager of the bufferassociated with the I/O(s) shared with adjacent filters. One reason isto ensure that all of the buffers are of the same size and share commonattributes so that a buffer associated with any input 402 may be sharedwith any output 404, thereby reducing the need to copy memory contentsbetween individual buffers associated with such inputs/outputs. Ifmatrix switch 308 cannot be an allocator for a given output (404),communication from an input (402) to that output is performed using aconventional memory copy operation between the individual buffersassociated with the select input/output.

As introduced above, the matrix switch programming grid 406 isdynamically generated by render engine 222 based, at least in part, onthe user-defined development project. As will be developed below, renderengine 222 invokes an instance of filter graph manager to assembles atree structure of an editing project, noting dependencies betweensource, filters and time to dynamically generate the programming grid406. A data structure comprising an example programming grid 406 isintroduced with reference to FIG. 5, below.

Turning briefly to FIG. 5, a graphical representation of a datastructure comprising an example programming grid 406 is presented, inaccordance with one embodiment of the present invention. In accordancewith the illustrated example embodiment of FIG. 5, programming grid 406is depicted as a two-dimensional data structure comprising a columnalong the y-axis 502 of the grid denoting input pins associated with acontent chain (e.g., series of filters to process media content) of thedevelopment project. The top row along the x-axis 504 of the datastructure denotes project time. With these grid “borders”, the body 506of the grid 406 is populated with output pin assignments, denoting whichinput pin is coupled to which output pin during execution of thedevelopment project. In this way, render engine 222 dynamicallygenerates and facilitates matrix switch 308. Those skilled in the artwill appreciate, however, that data structures of greater or lessercomplexity may well be used in support of the programming grid 406without deviating from the spirit and scope of the present invention.

Returning to FIG. 4, matrix switch 308 is also depicted with a pluralityof input/output buffers 408, shared among all of the input(s)/ouptut(s)(402, 404) to facilitate advanced processing features. That is, whilenot required to implement the core features of matrix switch 308, I/Obuffers 408 facilitate a number of innovative performance enhancingfeatures to improve the performance (or at least the user's perceptionof performance) of the processing system, thereby providing an improveduser experience. According to one implementation, I/O buffers 408 areseparate from the buffers assigned to each individual input and outputpin in support of communication through the switch. According to oneimplementation, I/O buffers 408 are primarily used to foster look-aheadprocessing of the project. Assume, for example, that a large portion ofthe media processing project required only 50% of the availableprocessing power, while some smaller portion required 150% of theavailable processing power. Implementation of the shared I/O buffers 408enable filter graph manager to execute tasks ahead of schedule andbuffer this content in the shared I/O buffers 408 until required. Thus,when execution of the filter graph reaches a point where more than 100%of the available processing power is required, the processing system cancontinue to supply content from the I/O buffers 408, while the systemcompletes execution of the CPU-intensive tasks. If enough shared bufferspace is provided, the user should never know that some tasks were notperformed in real-time. According to one implementation, shared buffers408 are dynamically split into two groups by render engine 222, a firstgroup supports the input(s) 402, while a second (often smaller) group isused in support of a primary output (e.g., output pin 1) to facilitate asecond, independent output processing thread. The use of an independentoutput buffers the render engine from processing delays that might occurin upstream and/or downstream filters, as discussed above. It will beappreciated by those skilled in the art that such that matrix switch 308and the foregoing described architecture beneficially suited to supportmedia streaming applications.

As introduced above, the filter graph is time-aware in the sense thatmedia (source) time and project execution time are maintained. Accordingto one implementation, matrix switch 308 maintains at least the projectclock, while an upstream filter maintains the source time, convertingbetween source and project time for all downstream filters (i.e.,including the matrix switch 308). According to one implementation, theframe rate converter filter of a filter graph is responsible forconverting source time to project time, and vice versa, i.e., supportingrandom seeks, etc. Alternatively, matrix switch 308 utilizes anintegrated set of clock(s) to independently maintain project and mediatimes.

Having introduced the architectural and operational elements of matrixswitch filter 308, FIG. 6 graphically illustrates an example filtergraph implementation incorporating the innovative matrix switch 308. Inaccordance with the illustrated example embodiment, filter graph 600 isgenerated by render engine 222 in response to a user defined developmentproject. Unlike the lengthy linear filter graphs typical of conventiondevelopment systems however, filter graph 600 is shown incorporating amatrix switch filter 308 to recursively route the pre-processed content(e.g., through filters 602, 606, 610, 614 and 618, described more fullybelow) through a user-defined number of transform filters including, forexample, transition filter(s) 620 and effects filter(s) 622. Moreover,as will be developed more fully below, the scalable nature of matrixswitch filter 308 facilitates such iterative processing for any numberof content threads, tracks or compositions.

According to one implementation, a matrix switch filter 308 can onlyprocess one type of media content, of the same size and at the sameframe-rate (video) or modulation type/schema (audio). Thus, FIG. 6 isdepicted comprising pre-processing filters with a parser filter 606 toseparate, independent content type(s) (e.g., audio content and videocontent), wherein one of the media types would be processed along adifferent path including a separate instance of matrix switch 308. Thus,in accordance with the illustrated example embodiment of a mediaprocessing system, processing multimedia content including audio andvideo would utilize two (2) matrix switch filters 308, one dedicated toaudio processing (not shown) and one dedicated to video processing. Thatis not to say, however, that multiple switch filters 308 could not beused (e.g., two each for audio and video) for each content type inalternate implementations. Similarly, it is anticipated that inalternate implementations a matrix switch 308 that accepts multiplemedia types could well be used without deviating from the spirit andscope of the present invention.

In addition filter graph 600 includes a decoder filter 610 to decode themedia content. Resize filter 614 is employed when matrix switch 308 isto receive content from multiple sources, ensuring that the size of thereceived content is the same, regardless of the source. According to oneimplementation, resize filter 614 is selectively employed in videoprocessing paths to adjust the media size of content from one or moresources to a user-defined level. Alternatively, resizer filter 614adjusts the media size to the largest size provided by any one or moremedia sources. That is, if, for example, render engine 222 identifiesthe largest required media size (e.g., 1270×1040 video pixels per frame)and, for any content source not providing content at this size, thecontent is modified (e.g., stretched, packed, etc.) to fill this sizerequirement. The frame rate converter (FRC) and pack filter 618,introduced above, ensures that video content from the multiple sourcesis arriving at the same frame rate, e.g., ten (10) frames per second. Asintroduced above, the FRC also maintains the distinction between sourcetime and project time.

In accordance with one aspect of the present invention, filter graph 600is depicted utilizing a single, negotiated buffer 604, 608, 612, 616,etc. between adjacent filters. In this regard, render engine 222 reducesthe buffer memory requirements in support of a development project.

From the point of pre-processing (filters 602, 606, 610, 614, 618),rather than continue a linear filter graph incorporating all of thetransition 620 and effect 622 filter(s), render engine 222 utilizes acascade architecture, recursively passing media content through thematrix switch 308 to apply to the transform filter(s) (e.g., 620, 622,etc.) to complete the execution of the development project. It will beappreciated by those skilled in the art that the ability to recursivelypass media content through one or more effect and/or transition filtersprovided by the matrix switch filter 308 greatly reduces the perceivedcomplexity of otherwise large filter graphs, while reducing memory andcomputational overhead.

Turning to FIG. 7, a flow chart of an example method for generating afilter graph is presented, in accordance with one aspect of the presentinvention. The method 700 begins with block 702 wherein render engine222 receives an indication to generate a filter graph representing auser-defined development project (e.g., a media editing project).According to one example implementation, the indication is received froman application 224 via COM interface(s) 302.

In block 704, render engine 222 facilitates generation of the editingproject, identifying the number and type of media sources selected bythe user. In block 706, based at least in part on the number and/or typeof media sources, filter graph manger 222 exposes source, transform andrendering filter(s) to effect a user defined media processing project,while beginning to establish a programming grid 406 for the matrixswitch filter 308.

In block 708, reflecting user editing instructions, render engine 222completes the programming grid 406 for matrix switch 308, identifyingwhich inputs 402 are to be coupled to which outputs 404 at particularproject times.

Based, at least in part, on the programming grid 406 render engine 222generates a matrix switch filter 308 with an appropriate number of input402 and output 404 pins to effect the project, and assembles the filtergraph, block 710.

In block 712, to reduce the buffer memory requirements for theprocessing project, the render engine 222 instructs the filterspopulating the filter graph to (re)negotiate buffer memory requirementsbetween filters. That is, adjacent filters attempt to negotiate a sizeand attribute standard so that a single buffer can be utilized to coupleeach an output pin of one filter to an input pin of a downstream filter.An example implementation of the buffer negotiation process of block 712is presented in greater detail with reference to FIG. 8.

Turning briefly to FIG. 8, an example method of negotiating bufferrequirements between adjacent filters is presented, in accordance withone example implementation of the present invention. Once the finalconnection is established to matrix switch 308, matrix switch 308identifies the maximum buffer requirements for any filter coupled to anyof its pins (input 402 and/or output 404), block 802. According to oneimplementation, the maximum buffer requirements are defined as thelowest common multiple of buffer alignment requirements, and the maximumof all the pre-fix requirements of the filter buffers.

In block 804, matrix switch 308 selectively removes one or more existingfilter connections to adjacent filters. Matrix switch 308 thenreconnects all of its pins to adjacent filters using a common buffersize between each of the pins, block 806. In block 808, matrix switch308 negotiates to be the allocator for all of its pins (402, 404). Ifthe matrix switch 308 cannot, for whatever reason, be the allocator forany of its input pins 402 minimal loss to performance is encountered, asthe buffer associated with the input pin will still be compatible withany downstream filter (i.e., coupled to an output pin) and, thus, thebuffer can still be passed to the downstream filter without requiring amemory copy operation. If, however, matrix switch 308 cannot be anallocator for one of its output pins 404, media content must then betransferred to at least the downstream filter associated with thatoutput pin using a memory copy operation, block 810.

In block 812, once the matrix switch 308 has re-established itsconnection to adjacent filters, render engine 222 restores theconnection in remaining filters using negotiated buffer requirementsemanating from the matrix switch filter 308 buffer negotiations. Oncethe connections throughout the filter graph have been reconnected, theprocess continues with block 714 of FIG. 7.

In block 714 (FIG. 7), have re-established the connections betweenfilters, render engine 222 is ready to implement a user's instruction toexecute the media processing project.

Example Operation and Implementation(s)

The matrix switch described above is quite useful in that it allowsmultiple inputs to be directed to multiple outputs at any one time.These input can compete for a matrix switch output. The embodimentsdescribed below permit these competing inputs to be organized so thatthe inputs smoothly flow through the matrix switch to provide a desiredoutput. And, while the inventive programming techniques are described inconnection with the matrix switch as such is employed in the context ofmulti-media editing projects, it should be clearly understood thatapplication of the inventive programming techniques and structuresshould not be so limited only to application in the field of multi-mediaediting projects or, for that matter, multi-media applications or datastreams. Accordingly, the principles about to be discussed can beapplied to other fields of endeavor in which multiple inputs can becharacterized as competing for a particular output during a common timeperiod.

In the multi-media example below, the primary output of the matrixswitch is a data stream that defines an editing project that has beencreated by a user. Recall that this editing project can include multipledifferent sources that are combined in any number of different ways, andthe sources that make up a project can comprise audio sources, videosources, or both. The organization of the inputs and outputs of thematrix switch are made manageable, in the examples described below, by adata structure that permits the matrix switch to be programmed.

FIG. 9 shows an overview of a process that takes a user-defined editingproject and renders from it a data structure that can be used to programthe matrix switch.

Specifically, a user-defined editing project is shown generally at 900.Typically, when a user creates an editing project, they can select froma number of different multimedia clips that they can then assemble intoa unique presentation. Each individual clip represents a source ofdigital data or a source stream (e.g., multimedia content). Projects caninclude one or more sources 902. In defining their project, a user canoperate on sources in different ways. For example, video sources canhave transitions 904 and effects 906 applied on them. A transitionobject is a way to change between two or more sources. As discussedabove, a transition essentially receives as input, two or more streams,operates on them in some way, and produces a single output stream. Anexemplary transition can comprise, for example, fading from one sourceto another. An effect object can operate on a single source or on acomposite of sources. An effect essentially receives a single inputstream, operates on it in some way, and produces a single output stream.An exemplary effect can comprise a black-and-white effect in which avideo stream that is configured for presentation in color format isrendered into a video stream that is configured for presentation inblack and white format. Unlike conventional effect filters, effectobject 906 may well perform multiple effect tasks. That is, inaccordance with one implementation, an effect object (e.g., 906) mayactually perform multiple tasks on the received input stream, whereinsaid tasks would require multiple effect filters in a conventionalfilter graph system.

An exemplary user interface 908 is shown and represents what a usermight see when they produce a multimedia project with software executingon a computer. In this example, the user has selected three sources A,B, and C, and has assembled the sources into a project timeline. Theproject timeline defines when the individual sources are to be rendered,as well as when any transitions and/or effects are to occur.

In the discussion that follows, the notion of a track is introduced. Atrack can contain one or more sources or source clips. If a trackcontains more than one source clip, the source clips cannot overlap. Ifsource clips are to overlap (e.g. fading from one source to another, orhaving one source obscure another), then multiple tracks are used. Atrack can thus logically represent a layer on which sequential video isproduced. User interface 908 illustrates a project that utilizes threetracks, each of which contains a different source. In this particularproject source A will show for a period of time. At a defined time inthe presentation, source A is obscured by source B. At some later time,source B transitions to source C.

In accordance with the described embodiment, the user-defined editingproject 900 is translated into a data structure 910 that represents theproject. In the illustrated and described example, this data structure910 comprises a tree structure. It is to be understood, however, thatother data structures could be used. The use of tree structures torepresent editing projects is well-known and is not described here inany additional detail. Once the data structure 910 is defined, it isprocessed to provide a data structure 912 that is utilized to programthe matrix switch. In the illustrated and described embodiment, datastructure 912 comprises a grid from which the matrix switch can beprogrammed. It is to be understood and appreciated that other datastructures and techniques could, however, be used to program the matrixswitch without departing from the spirit and scope of the claimedsubject matter.

The processing that takes place to define data structures 910 and 912can take place using any suitable hardware, software, firmware, orcombination thereof. In the examples set forth below, the processingtakes place utilizing software in the form of a video editing softwarepackage that is executable on a general purpose computer.

Example Project

For purposes of explanation, consider FIG. 10 which shows project 908from FIG. 9 in a little additional detail. Here, a time line containingnumbers 0-16 is provided adjacent the project to indicate whenparticular sources are to be seen and when transitions and effects (whenpresent) are to occur. In the examples in this document, the followingconvention exists with respect to projects, such as project 908. Apriority exists for video portions of the project such that as oneproceeds from top to bottom, the priority increases. Thus, in the FIG.10 example, source A has the lowest priority followed by source B andsource C. Thus, if there is an overlap between higher and lower prioritysources, the higher priority source will prevail. For example, source Bwill obscure source A from between t=4-8.

In this example, the following can be ascertained from the project 908and time line: from time t=0-4 source A should be routed to the matrixswitch's primary output; from t=4-12 source B should be routed to thematrix switch's primary output; from t=12-14 there should be atransition between source B and source C which should be routed to thematrix switch's primary output; and from t=14-16 source C should berouted to the matrix switch's primary output. Thus, relative to thematrix switch, each of the sources and the transition can becharacterized by where it is to be routed at any given time. Consider,for example, the table just below:

Object Routing for a given time C t = 0-12 (nowhere); t = 12-14(transition); t = 14-16 (primary output) B t = 0-4 (nowhere); t = 4-12(primary output); t = 12-14 (transition); t = 14-16 (nowhere) A t = 0-4(primary output); t = 4-16 (nowhere) Transition t = 0-12 (nowhere); t =12-14 (primary output); t = 14-16 (nowhere)

FIG. 11 shows an exemplary matrix switch 1100 that can be utilized inthe presentation of the user's project. Matrix switch 1100 comprisesmultiple inputs and multiple outputs. Recall that a characteristic ofthe matrix switch 1100 is that any of the inputs can be routed to any ofthe outputs at any given time. A transition element 1102 is provided andrepresents the transition that is to occur between sources B and C.Notice that the matrix switch includes four inputs numbered 0-3 andthree outputs numbered 0-2. Inputs 0-2 correspond respectively tosources A-C, while input 3 corresponds to the output of the transitionelement 1102. Output 0 corresponds to the switch's primary output, whileoutputs 1 and 2 are routed to the transition element 1102.

The information that is contained in the table above is the informationthat is utilized to program the matrix switch. The discussion presentedbelow describes but one implementation in which the informationcontained in the above table can be derived from the user's project timeline.

Recall that as a user edits or creates a project, software thatcomprises a part of their editing software builds a data structure thatrepresents the project. In the FIG. 9 overview, this was data structure910. In addition to building the data structure that represents theediting project, the software also builds and configures a matrix switchthat is to be used to define the output stream that embodies theproject. Building and configuring the matrix switch can include buildingthe appropriate graphs (e.g., a collection of software objects, orfilters) that are associated with each of the sources and associatingthose graphs with the correct inputs of the matrix switch. In addition,building and configuring the matrix switch can also include obtainingand incorporating additional appropriate filters with the matrix switch,e.g. filters for transitions, effects, and mixing (for audio streams).This will become more apparent below.

FIG. 12 shows a graphic representation of an exemplary data structure1200 that represents the project of FIG. 10. Here, the data structurecomprises a traditional hierarchical tree structure. Any suitable datastructure can, however, be utilized. The top node 1202 constitutes agroup node. A group encapsulates a type of media. For example, in thepresent example the media type comprises video. Another media type isaudio. The group node can have child nodes that are either tracks orcomposites. In the present example, three track nodes 1204, 1206, and1208 are shown. Recall that each track can have one or more sources. Ifa track comprises more than one source, the sources cannot overlap.Here, all of the sources (A, B, and C) overlap. Hence, three differenttracks are utilized for the sources. In terms of priority, the lowestpriority source is placed into the tree furthest from the left at 1204a. The other sources are similarly placed. Notice that source C (1208 a)has a transition 1210 associated with it. A transition object, in thisexample, defines a two-input/one output operation. When applied to atrack or a composition (discussed below in more detail), the transitionobject will operate between the track to which it has been applied, andany objects that are beneath it in priority and at the same level in thetree. A “tree level” has a common depth within the tree and belongs tothe same parent. Accordingly, in this example, the transition 1210 willoperate on a source to the left of the track on which source C resides,and beneath it in priority, i.e. source B. If the transition is appliedto any object that has nothing beneath it in the tree, it willtransition from blackness (and/or silence if audio is included).

Once a data structure representing the project has been built, in thiscase a hierarchical tree structure, a rendering engine processes thedata structure to provide another data structure that is utilized toprogram the matrix switch. In the FIG. 9 example, this additional datastructure is represented at 912. It will be appreciated and understoodthat the nodes of tree 1200 can include so-called meta information suchas a name, ID, and a time value that represents when that particularnode's object desires to be routed to the output, e.g. node 1204 a wouldinclude an identifier for the node associating it with source A, as wellas a time value that indicates that source A desires to be routed to theoutput from time t=0-8. This meta information is utilized to build thedata structure that is, in turn, utilized to program the matrix switch.

In the example about to be described below, a specific data structure inthe form of a grid is utilized. In addition, certain specifics aredescribed with respect to how the grid is processed so that the matrixswitch can be programmed. It is to be understood that the specificdescribed approach is for exemplary purposes only and is not intended tolimit application of the claims. Rather, the specific approachconstitutes but one way of implementing broader conceptual notionsembodied by the inventive subject matter.

FIGS. 13-18 represent a process through which the inventive grid isbuilt. In the grid about to be described, the x axis represents time,and the y axis represents layers in terms of priority that go fromlowest (at the top of the grid) to highest (at the bottom of the grid).Every row in the grid represents the video layer. Additionally, entriesmade within the grid represent output pins of the matrix switch. Thiswill become apparent below.

The way that the grid is built in this example is that the renderingengine does a traversal operation on the tree 1200. In this particularexample, the traversal operation is known as a “depth-first,left-to-right” traversal. This operation will layerize the nodes so thatthe leftmost track or source has the lowest priority and so on. Doingthe above-mentioned traversal on tree 1200 (FIG. 12), the first nodeencountered is node 1204 which is associated with source A. This is thelowest priority track or source. A first row is defined for the grid andis associated with source A. After the first grid row is defined, a gridentry is made and represents the time period for which source A desiresto be routed to the matrix switch's primary output.

FIG. 13 shows the state of a grid 1300 after this first processing step.Notice that from time t=0-8, a “0” has been placed in the grid. The “0”represents the output pin of the matrix switch—in this case the primaryoutput. Next, the traversal encounters node 1206 (FIG. 12) which isassociated with source B. A second row is thus defined for the grid andis associated with source B. After the second grid row is defined, agrid entry is made and represents the time period for which source Bdesires to be routed to the matrix switch's primary output.

FIG. 14 shows the state of grid 1300 after this second processing step.Notice that from time t=4-14, a “0” has been placed in the grid. Noticeat this point that something interesting has occurred which will beresolved below. Each of the layers has a common period of time (i.e.t=4-8) for which it desires to be routed to the matrix switch's primaryoutput. However, because of the nature of the matrix switch, only oneinput can be routed to the primary output at a time. Next, the traversalencounters node 1208 (FIG. 12) which is associated with source C. Inthis particular processing example, a rule is defined that sources ontracks are processed before transitions on the tracks are processedbecause transitions operate on two objects that are beneath them. Athird row is thus defined for the grid and is associated with source C.After the third row is defined, a grid entry is made and represents thetime period for which source C desires to be routed to the matrixswitch's primary output.

FIG. 15 shows the state of grid 1300 after this third processing step.Notice that from time t=12-16, a “0” has been placed in the grid. Next,the traversal encounters node 1210 (FIG. 12) which corresponds to thetransition. Thus, a fourth row is defined in the grid and is associatedwith the transition. After the fourth row is defined, a grid entry ismade and represents the time period for which the transition desires tobe routed to the matrix switch's primary output.

FIG. 16 shows the state of grid 1300 after this fourth processing step.Notice that from time t=12-14, a “0” has been placed in the grid for thetransition entry. The transition is a special grid entry. Recall thatthe transition is programmed to operate on two inputs and provide asingle output. Accordingly, starting at the transition entry in the gridand working backward, each of the entries corresponding to the same treelevel are examined to ascertain whether they contain entries thatindicate that they want to be routed to the output during the same timethat the transition is to be routed to the output. If grid entries arefound that conflict with the transition's grid entry, the conflictinggrid entry is changed to a value to corresponds to an output pin thatserves as an input to the transition element 1102 (FIG. 11). This isessentially a redirection operation. In the illustrated grid example,the transition first finds the level that corresponds to source C. Thislevel conflicts with the transition's grid entry for the time periodt=12-14. Thus, for this time period, the grid entry for level C ischanged to a switch output that corresponds to an input for thetransition element. In this example, a “2” is placed in the grid tosignify that for this given time period, this input is routed to outputpin 2. Similarly, continuing up the grid, the next level that conflictswith the transition's grid entry is the level that corresponds to sourceB. Thus, for the conflicting time period, the grid entry for level B ischanged to a switch output that corresponds to an input for thetransition element. In this example, a “1” is placed in the grid tosignify that for this given time period, this input is routed to outputpin 1 of the matrix switch.

FIG. 17 shows the state of the grid at this point in the processing.Next, a pruning function is implemented which removes any other lowerpriority entry that is contending for the output with a higher priorityentry. In the example, the portion of A from t=4-8 gets removed becausethe higher priority B wants the output for that time.

FIG. 18 shows the grid with a cross-hatched area that signifies thatportion of A's grid entry that has been removed.

At this point, the grid is in a state in which it can be used to programthe matrix switch. The left side entries—A, B, C, and TRANS representinput pin numbers 0, 1, 2, and 3 (as shown) respectively, on the matrixswitch shown in FIG. 11. The output pin numbers of the matrix switch aredesignated at 0, 1, and 2 both on the switch in FIG. 11 and within thegrid in FIG. 18. As one proceeds through the grid, starting with sourceA, the programming of the matrix switch can be ascertained as follows: Ais routed to output pin 0 of the matrix switch (the primary output) fromt=0-4. From t=4-16, A is not routed to any output pins. From t=0-4, B isnot routed to any of the output pins of the matrix switch. From t=4-12,B is routed to the primary output pin 0 of the matrix switch. Fromt=12-14, B is routed to output pin 1 of the matrix switch. Output pin 1of the matrix switch corresponds to one of the input pins for thetransition element 1102 (FIG. 11). From t=14-16, B is not routed to anyof the output pins of the matrix switch. From t=0-12, C is not routed toany of the output pins of the matrix switch. From t=12-14, C is routedto output pin 2 of the matrix switch. Output pin 2 of the matrix switchcorresponds to one of the input pins for the transition element 302(FIG. 3). From t=12-14 the transition element (input pin 3) is routed tooutput pin 0. From t=14-16, C is routed to output pin 0 of the matrixswitch.

As alluded to above, one of the innovative aspects of the matrix switch308 is its ability to seek to any point in a source, without having toprocess the intervening content serially through the filter. Rather,matrix switch 308 identifies an appropriate transition point and dumpsat least a subset of the intervening content, and continues processingfrom the seeked point in the content.

The ability of the matrix switch 308 to seek to any point in the mediacontent gives rise to certain performance enhancement heretoforeunavailable in computer implemented media processing systems. Forexample, generation of a filter graph by render engine 222 may take intoaccount certain performance characteristics of the media processingsystem which will execute the user-defined media processing project. Inaccordance with this example implementation, render engine 222 mayaccess and analyze the system registry of the operating system, forexample, to ascertain the performance characteristics of hardware and/orsoftware elements of the computing system implementing the mediaprocessing system, and adjust the filter graph construction to improvethe perceived performance of the media processing system by the user.Nonetheless, there will always be a chance that a particular instance ofa filter graph will not be able to process the media stream fast enoughto provide the desired output at the desired time, i.e., processing ofthe media stream bogs down leading to delays at the rendering filter. Insuch a case, matrix switch 308 will recognize that it is not receivingmedia content at the appropriate project time, and may skip certainsections of the project in an effort to “catch-up” and continue theremainder of the project in real time. According to one implementation,when matrix switch 308 detects such a lag in processing, it will analyzethe degree of the lag and issue a seek command to the source (throughthe source processing chain) to a future point in the project, whereprocessing continues without processing any further content prior to theseeked point.

Thus, for the editing project depicted in FIG. 10, the processingdescribed above first builds a data structure (i.e. data structure 1200in FIG. 12) that represents the project in hierarchical space, and thenuses this data structure to define or create another data structure thatcan be utilized to program the matrix switch.

FIG. 19 is a flow diagram that describes steps in a method in accordancewith the described embodiment. The method can be implemented in anysuitable hardware, software, firmware, or combination thereof. In theillustrated and described embodiment, the method is implemented insoftware.

Step 1900 provides a matrix switch. An exemplary matrix switch isdescribed above. Step 1902 defines a first data structure thatrepresents the editing project. Any suitable data structure can be used,as will be apparent to those of skill in the art. In the illustrated anddescribed embodiment, the data structure comprises a hierarchical treestructure having nodes that can represent tracks (having one or moresources), composites, transitions and effects. Step 1904 processes thefirst data structure to provide a second data structure that isconfigured to program the matrix switch. Any suitable data structure canbe utilized to implement the second data structure. In the illustratedand described embodiment, a grid structure is utilized. Exemplaryprocessing techniques for processing the first data structure to providethe second data structure are described above. Step 1906 then uses thesecond data structure to program the matrix switch.

Example Project with a Transition and an Effect

Consider project 2000 depicted in FIG. 20. In this project there arethree tracks, each of which contains a source, i.e. source A, B and C.This project includes an effect applied on source B and a transitionbetween sources B and C. The times are indicated as shown.

As the user creates their project, a data structure representing theproject is built. FIG. 21 shows an exemplary data structure in the formof a hierarchical tree 2100 that represents project 2000. There, thedata structure includes three tracks, each of which contains one of thesources. The sources are arranged in the tree structure in the order oftheir priority, starting with the lowest priority source on the left andproceeding to the right. There is an effect (i.e. “Fx”) that is attachedto or otherwise associated with source B. Additionally, there is atransition attached to or otherwise associated with source C.

In building the grid for project 2000, the following rule is employedfor effects. An effect, in this example, is a one-input/one-outputobject that is applied is to one object—in this case source B. When theeffect is inserted into the grid, it looks for any one object beneath itin priority that has a desire to be routed to the primary output of thematrix switch at the same time. When it finds a suitable object, itredirects that object's output from the matrix switch's primary outputto an output associated with the effect.

As an example, consider FIG. 22 and the grid 2200. At this point in theprocessing of tree 2100, the rendering engine has incorporated entriesin the grid corresponding to sources A, B and the effect. It has done soby traversing the tree 2100 in the above-described way. In this example,the effect has already looked for an object beneath it in priority thatis competing for the primary output of the matrix switch. It found anentry for source B and then redirected B's grid entry to a matrix switchoutput pin that corresponds to the effect—here output pin 1.

As the render engine 222 completes its traversal of tree 2100, itcompletes the grid. FIG. 23 shows a completed grid 2200. Processing ofthe grid after that which is indicated in FIG. 22 takes placesubstantially as described above with respect to the first example.Summarizing, this processing though: after the effect is entered intothe grid and processed as described above, the traversal of tree 2100next encounters the node associated with source C. Thus, a row is addedin the grid for source C and an entry is made to indicate that source Cdesires the output from t=12-16. Next, the tree traversal encounters thenode associated with the transition. Accordingly, a row is added to thegrid for the transition and a grid entry is made to indicate that thetransition desires the output from t=12-14. Now, as described above, thegrid is examined to find two entries, lower in priority than thetransition and located at the same tree level as the transition, thatcompete for the primary output of the matrix switch. Here, those entriescorrespond to the grid entries for the effect and source C that occurfrom t=12-14. These grid entries are thus redirected to output pins ofthe matrix switch 308 that correspond to the transition—here pins 2 and3 as indicated. Next, the grid is pruned which, in this example, removesa portion of the grid entry corresponding to source A for t=4-8 becauseof a conflict with the higher-priority entry for source B.

FIG. 24 shows the resultant matrix switch that has been built andconfigured as the grid was being processed above. At this point, thegrid can be used to program the matrix switch. From the grid picture, itis very easy to see how the matrix switch 308 is going to be programmed.Source A will be routed to the matrix switch's primary output (pin 0)from t=0-4; source B will be redirected to output pin 1 (effect) fromt=4-14 and the effect on B will be routed to the output pin 0 fromt=4-12. From t=12-14, the effect and source C will be routed to outputpins corresponding to the transition (pins 2 and 3) and, accordingly,during this time the transition (input pin 4) will be routed to theprimary output (output pin 0) of the matrix switch. From t=14-16, sourceC will be routed to the primary output of the matrix switch.

It will be appreciated that as the software, in this case the renderengine 222, traverses the tree structure that represents a project, italso builds the appropriate graphs and adds the appropriate filters andgraphs to the matrix switch. Thus, for example, as the render engine 222encounters a tree node associated with source A, in addition to addingan entry to the appropriate grid, the software builds the appropriategraphs (i.e. collection of linked filters), and associates those filterswith an input of the matrix switch. Similarly, when the render engine222 encounters an effect node in the tree, the software obtains aneffect object or filter and associates it with the appropriate output ofthe matrix switch. Thus, in the above examples, traversal of the treestructure representing the project also enables the software toconstruct the appropriate graphs and obtain the appropriate objects andassociate those items with the appropriate inputs/outputs of the matrixswitch 308. Upon completion of the tree traversal and processing of thegrid, an appropriate matrix switch has been constructed, and theprogramming (i.e. timing) of inputs to outputs for the matrix switch hasbeen completed.

Treatment of “Blanks” in a Project

There may be instances in a project when a user leaves a blank in theproject time line. During this blank period, no video or audio isscheduled for play.

FIG. 25 shows a project that has such a blank incorporated therein. Ifthere is such a blank left in a project, the software is configured toobtain a “black” source and associate the source with the matrix switchat the appropriate input pin. The grid is then configured when it isbuilt to route the black source to the output at the appropriate timesand fade from the black (and silent) source to the next source at theappropriate times. The black source can also be used if there is atransition placed on a source for which there is no additional sourcefrom which to transition.

Audio Mixing

In the examples discussed above, sources comprising video streams werediscussed. In those examples, at any one time, only two video streamswere combined into one video stream. However, each project can, andusually does contain an audio component. Alternately, a project cancontain only an audio component. The audio component can typicallycomprise a number of different audio streams that are combined. Thediscussion below sets forth but one way of processing and combiningaudio streams.

In the illustrated example, there is no limit on the number of audiostreams that can be combined at any one time.

Suppose, for example, there is an audio project that comprises 5 tracks,A-E. FIG. 26 shows an exemplary project. The shaded portions of eachtrack represent the time during which the track is not playing. So, forexample, at t=0-4, tracks B, D, and E are mixed together and will play.From t=4-10, tracks A-E are mixed together and will play, and the like.

FIG. 27 shows the grid for this project at 2700. Since we are dealingwith this composition now, all of the effects and transitions includingthe audio mixing are only allowed to affect things in this composition.Thus, there is the concept of a boundary 2702 that prevents any actionsor operations in this composition from affecting any other grid entries.Note that there are other entries in the grid and that thepresently-illustrated entries represent only those portions of theproject that relate to the audio mixing function.

Grid 2700 is essentially set up in a manner similar to that describedabove with respect to the video projects. That is, for each track, a rowis added to the grid and a grid entry is made for the time period duringwhich the source on that track desires to be routed to the primaryoutput of the matrix switch. In the present example, grid entries aremade for sources A-E. Next, in the same way that a transition or effectwas allocated a row in the grid, a “mix” element is allocated a row inthe grid as shown and a grid entry is made to indicate that the mixelement desires to be routed to the primary output of the matrix switchfor a period of time during which two or more sources compete for thematrix switch's primary output. Note that in this embodiment, allocationof a grid row for the mix element can be implied. Specifically, whereasin the case of a video project, overlapping sources simply result inplaying the higher priority source (unless the user defines a transitionbetween them), in the audio realm, overlapping sources are treated as animplicit request to mix them. Thus, the mix element is allocated a gridrow any time there are two or more overlapping sources.

Once the mix element is allocated into the grid, the grid is processedto redirect any conflicting source entries to matrix switch output pinsthat correspond to the mix element. In the above case, redirection ofthe grid entries starts with pin 3 and proceeds through to pin 7. Thecorresponding matrix switch is shown in FIG. 28. Notice that all of thesources are now redirected through the mix element which is amulti-input/one output element. The mix element's output is fed backaround and becomes input pin 15 of the matrix switch. All of theprogramming of the matrix switch is now reflected in the grid 2700.Specifically, for the indicated time period in the grid, each of thesources is routed to the mix element which, in turn, mixes theappropriate audio streams and presents them to the primary output pin 0of the matrix switch.

Compositions

There are situations that can arise when building an editing projectwhere it would be desirable to apply an effect or a transition on just asubset of a particular project or track. Yet, there is no practicableway to incorporate the desired effect or transition. In the past,attempts to provide added flexibility for editing projects have beenmade in the form of so called “bounce tracks”, as will be appreciatedand understood by those of skill in the art. The use of bounce tracksessentially involves processing various video layers (i.e. tracks),writing or moving the processed layers or tracks to another location,and retrieving the processed layers when later needed for additionalprocessing with other layers or tracks. This type of processing can beslow and inefficient.

To provide added flexibility and efficiency for multi-media editingprojects, the notion of a composite or composition is introduced. Acomposite or composition can be considered as a representation of anediting project as a single track. Recall that editing projects can haveone or more tracks, and each track can be associated with one or moresources that can have effects applied on them or transitions betweenthem. In addition, compositions can be nested inside one another.

Example Project with Composite

Consider, for example, FIG. 29 which illustrates an exemplary project2900 having a composition 2902. In this example, composition 2902comprises sources B and C and a transition between B and C that occursbetween t=12-14. This composition is treated as an individual track orlayer. Project 2900 also includes a source A, and a transition betweensource A and composition 2902 at t=4-8. It will be appreciated thatcompositions can be much more complicated than the illustratedcomposition, which is provided for exemplary purposes only. Compositionsare useful because they allow the grouping of a particular set ofoperations on one or more tracks. The operation set is performed on thegrouping, and does not affect tracks that are not within the grouping.To draw an analogy, a composition is similar in principle to amathematical parenthesis. Those operations that appear within theparenthesis are carried out in conjunction with those operations thatare intended to operate of the subject matter of the parenthesis. Theoperations within the parenthesis do not affect tracks that do notappear within the parenthesis.

In accordance with the processing that is described above in connectionwith FIG. 19, a first data structure is defined that represents theediting project. FIG. 30 shows an exemplary data structure 3000 in theform of a hierarchical tree structure. In this example, group node 3002includes two children—track node 3004 and composite node 3006. Tracknode 3004 is associated with source A. Composite node 3006 includes twochildren—track nodes 3008 and 3010 that are respectively associated withsources B (3008 a) and C (3010 a). A transition T2 (3012) is applied onsource C and a transition T1 (3014) is applied on composition 3006.

Next, data structure 3000 is processed to provide a second datastructure that is configured to program the matrix switch. Note that asthe data structure is being programmed, a matrix switch is being builtand configured at the same time. In this example, the second datastructure comprises a grid structure that is assembled in much the sameway as was described above. There are, however, some differences and,for purposes of understanding, the complete evolution of the gridstructure is described here. In the discussion that follows, thecompleted matrix switch is shown in FIG. 38.

When the rendering engine initiates the depth-first, left-to-righttraversal of data structure 3000, the first node it encounters is tracknode 3004 which is associated with source A. Thus, a first row of thegrid is defined and a grid entry is made that represents the time periodfor which source A desires to be routed to the matrix switch's primaryoutput pin.

FIG. 31 shows the state of a grid 3100 after this first processing step.Next the traversal of data structure 3000 encounters the composite node3006. The composite node is associated with two tracks—track 3008 andtrack 3010. Track 3008 is associated with source B. Accordingly, asecond row of the grid is defined and a grid entry is made thatrepresents the time period for which source B desires to be routed tothe matrix switch's primary output pin. Additionally, since B is amember of a composition, meta-information is contained in the grid thatindicates that this grid row defines one boundary of the composition.This meta-information is graphically depicted with a bracket thatappears to the left of the grid row.

FIG. 32 shows the state of grid 3100 after this processing step. Next,the traversal of data structure 3000 encounters node 3010 which isassociated with source C. Thus, a third row of the grid is added and agrid entry is made that represents the time period for which source Cdesires to be routed to the matrix switch's primary output pin.

FIG. 33 shows the state of grid 3100 after this processing step. Noticethat the bracket designating the composition now encompasses the gridrow associated with source C. The traversal next encounters node 3012which is the node associated with the second transition T2. Thus, as inthe above example, a grid row is added for the transition and a gridentry is made that represents the time period for which the transitiondesires to be routed to the matrix switch's primary output pin.

FIG. 34 shows the state of grid 3100 after this processing step. Noticethat the bracket designating the composition is now completed andencompasses grid row entries that correspond to sources B and C and thetransition between them. Recall from the examples above that atransition, in this example, is programmed to operate on two inputs andprovide a single output. In this instance, and because the transitionoccurs within a composition, the transition is constrained by a rulethat does not allow it to operate on any elements outside of thecomposition. Thus, starting at the transition entry and working backwardthrough the grid, entries at the same tree level and within thecomposition (as designated by the bracket) are examined to ascertainwhether they contain entries that indicate that they want to be routedto the output during the same time that the transition is to be routedto the output. Here, both of the entries for sources B and C haveportions that conflict with the transition's entry. Accordingly, thoseportions of the grid entries for sources B and C are redirected orchanged to correspond to output pins that are associated with atransition element that corresponds to transition T2.

FIG. 35 shows the state of grid 3100 after this processing step. Thetraversal next encounters node 3014 which is the node that is associatedwith the transition that occurs between source A and composition 2902(FIG. 29). Processing of this transition is similar to processing of thetransition immediately above except for the fact that the transitiondoes not occur within the composition. Because the transition occursbetween the composition and another source, one of the inputs for thetransition will be the composition, and one of the inputs will be sourceA (which is outside of the composition). Thus, a grid row is added forthis transition and a grid entry is made that represents the time periodfor which the transition desires to be routed to the matrix switch'sprimary output pin.

FIG. 36 shows the state of grid 3100 after this processing step. At thispoint then, the grid is examined for entries that conflict with theentry for transition T1. One conflicting grid entry is found for the rowthat corresponds to source B (inside the composition) and one thatcorresponds to source A (outside the composition). Accordingly, thoseportions of the grid row that conflict with transition T1 are changed orredirected to have values that are associated with output pins of thematrix switch that are themselves associated with a transition elementT1. In this example, redirection causes an entry of “3” and “4” to beinserted as shown.

FIG. 37 shows the state of grid 3100 after this processing step. Ifnecessary, a pruning operation would further ensure that the grid has nocompeting entries for the primary output of the matrix switch. Theassociated input pin numbers of the matrix switch are shown to the leftof grid 3100.

FIG. 38 shows a suitably configured matrix switch that has been build inaccordance with the processing described above. Recall that, as datastructure 3000 (FIG. 30) is processed by the rendering engine, a matrixswitch is built and configured in parallel with the building andprocessing of the grid structure that is utilized to program the matrixswitch. From the matrix switch and grid 3100 of FIG. 37, the programmingof the switch can be easily ascertained.

FIG. 38 a shows an exemplary data structure that represents a projectthat illustrates the usefulness of composites. In this example, theproject can mathematically be represented as follows:(Fx−noisy(A Tx−Blend B))Tx−Blend C

Here, an effect (noisy) is applied to A blended with B, the result ofwhich is applied to a blend with C. The composite in this example allowsthe grouping of the things beneath it so that the effect (noisy), whenit is applied, is applied to everything that is beneath it. Notice thatwithout the composite node, there is no node where an effect can beapplied that will affect (A Tx−Blend B). Hence, in this example,operations that appear within the parenthesis are carried out on tracksthat appear within the parenthesis. Those operations do not affecttracks that are not within the parenthesis.

FIG. 39 is a flow diagram that described steps in a method in accordancewith one embodiment. The method can be implemented in any suitablehardware, software, firmware, or combination thereof. In thepresently-described example, the method is implemented in software.

Step 3900 defines a multimedia editing project that includes at leastone composite. The composite represents multiple tracks as a singletrack for purposes of the processing described just below. It isimportant to note that, in the processing described just below, andbecause of the use of composites, the extra processing that is requiredby bounce tracks is avoided (i.e. operating on two tracks, moving theoperation result to another location, and retrieving the operationresult when later needed). This reduces the processing time that isrequired to render a multi-media project. Step 3902 defines a first datastructure that represents the editing project. Any suitable datastructure can be utilized. In the present example, a data structure inthe form of a hierarchical tree is utilized. An exemplary tree is shownin FIG. 30. Step 3904 processes the first data structure to provide asecond data structure that is configured to program a matrix switch. Inthe illustrated example, the second data structure comprises a gridstructure. Exemplary processing is described in the context of FIGS.30-37. Step 3906 then programs the matrix switch using the second datastructure.

Dynamic Graph Building

Having introduced the various architectural and implementation elementsof the present invention, above, attention is now drawn to FIGS. 40-44,wherein another aspect of the illustrated embodiment is presented. Asintroduced above, each matrix switch filter 308 is time aware. That is,according to one implementation, matrix switch 308 maintains one or bothproject time and media source time information. This enables the matrixswitch 308 to, among other things, throttle delivery of media content tothe matrix switch 308.

As an extension of this capability, in accordance with one aspect of thepresent invention, render engine 222, via matrix switch filter 308,dynamically builds a filter graph representation of a project duringexecution of the filter graph. That is, render engine 222 based, atleast in part by the control performed by matrix switch 308, dynamicallyloads filter graph chains as they are needed. Further, render engine 222may well discard, or cache processing chains when they are no longerrequired to support execution of the processing project. To illustratethe benefits afforded by dynamic graph building, assume, for example,that an editing project included over 100 sources, yet only three (3) ofthem were ever required at any given time to support execution of thefilter graph. Those skilled in the art will appreciate that loadingthree sources will be executed much fast than 100 sources, therebypermitting execution of the filter graph to commence much more rapidlythan conventional filter graph implementations. Further, the memory andprocessing resources required to support three (3) sources willgenerally be less than those required to support 100 sources. Thus,those skilled in the art will appreciate that the dynamic graph buildingproperties of the present invention reduce the computational and memoryrequirements placed on the host system (e.g., computing system 200).

FIG. 40 is a flow chart of an example method for processing mediacontent, in accordance with one embodiment of the present invention.More particularly, FIG. 40 illustrates an example method wherein renderengine 222 dynamically generates and manages a filter graph to reducethe computational and/or memory requirements placed on a host system. Asshown, method 4000 begins with block 4002, wherein render engine 222receives an indication to generate a development project. According toone implementation, as discussed above, render engine 222 receives theindication from a higher-level application 216, e.g., media processingapplication 224, to assist a user in generating a processing project(e.g., a media processing project).

In block 4004, render engine 222 identifies the number and nature of themedia sources within the user-defined processing project, in preparationfor generating a filter graph representation of the processing project.As introduced above, for each of the identified sources, render engine222 determines the necessary transform filters 306 required topre-process the source (i.e., the source processing chain), preparingthe chain for presentation to the matrix switch filter 308 and one ormore transition/effect filters 306. Unlike conventional implementationswhich would proceed to generate the entire filter graph in preparationfor execution of the processing project, render engine 222 generates alist of sources and when they are required in the filter graph. Anexample of a data structure comprising a list of processing chains ispresented with reference to FIG. 41.

Turning briefly to FIG. 41, a graphical illustration of an example datastructure comprising a processing chain execution list is presented. Asshown, the chain execution list 4100 is comprised of a number ofinformation fields, e.g., 4102-4110 which detail, in part, which chainsare required at a particular time in project execution. In accordancewith the illustrated example embodiment of FIG. 41, chain execution list4100 is depicted comprising a chain identifier field 4102, a sourceidentifier field 4104, a project time field 4106, a source time field4108, and a dependencies field 4110.

Upon identifying a project source and the associated filters requiredfor pre-processing the source (i.e., the source chain), render engine222 assigns the chain an identifier which uniquely identifies the sourcechain within the context of the filter graph. Accordingly, the chainexecution list 4100 includes a field 4102 which maintains a list of thechains utilized in the associated project. Within the context of thefilter graph, the chain identifier corresponds to the source and theassociated pre-processing filters.

The source identifier field 4104 contains information denoting theproject source associated with a particular chain identifier. In thisregard, the source identifier field 4104 may well contain a file name, afile handle, or any other suitable source identifier.

The project time field 4106 denotes at what point during projectexecution the source chain is required. The source time field 4108denotes what portion of the source file is required to support executionof the processing project. It should be appreciated that a user may wellutilize the whole source file or any part thereof, as defined by theprocessing project.

The dependencies field 4110 denotes whether the associated chain isdependent upon any other chain. As will be described in greater detailbelow, multiple chains may rely on a common source and/or a subset ofanother source chain. In certain implementations, it would not beadvantageous to unload source chains prior to their execution and/or theexecution of chains dependent thereon. Accordingly, render engine 222maintains a list of such dependencies within the chain execution list4100. It is to be appreciated, however, that certain circumstances mayarise where it is necessary to unload a chain prior to or duringexecution, or prior to execution of an otherwise dependent chain. Onesuch example is where the processing project utilizes a hierarchicalstructure, wherein individual chains are assigned a priority level. Animplementation is contemplated, for example, wherein the priority of aparticular chain is dynamically managed by a matrix switch filter 308within a filter graph based, at least in part, on how soon the chain isrequired to support the uninterrupted execution of the processingproject, i.e., chains which are required more urgently are assigned ahigher priority and, as a result, are processed at the disadvantage ofother, lower priority chains. In the extreme, lower priority chains areunloaded to enable loading of a higher priority chain. It is to beappreciated that, although depicted as a two-dimensional data structure,chain execution lists of greater or lesser complexity may well besubstituted without deviating from the spirit and scope of the presentinvention.

Returning to FIG. 40 and, in particular, block 4006, render engine 222dynamically generates and manages a filter graph representation of theprocessing project invoking only those chains associated with sourcesthat are necessary to support the current and/or impending execution ofthe filter graph. It is to be appreciated that by not opening each ofthe chains of a processing project, render engine 222 reduces the amountof memory required to build the filter graph, thereby reducing theamount of memory required to complete execution of the project, i.e.,recall the example where the entire graph utilized 100 sources, but onlyrequired three (3) at any given time. An example method of dynamicallygenerating and managing a filter graph is presented with reference tothe flow chart illustrated in FIG. 42.

Turning to FIG. 42, an example method for dynamically generating andmanaging a filter graph is presented, in accordance with one embodimentof the present invention. In accordance with the illustrated exampleimplementation of FIG. 42, method 4006 commences with block 4202 whereinrender engine 222 determines which chains are required to fulfillexecution of the development project for the next M seconds. Accordingto this example implementation, M must be greater than the minimum timeit takes to completely load the next chain. In accordance with theillustrated example implementation, wherein matrix switch filter 308controls the pace of project execution, matrix switch filter 308provides an indication to render engine 222 of what chains are requiredin block 4202.

According to one implementation, M is dynamically generated based on anumber of factors including, but not limited to, processing speed,available memory, the complexity of the development project, the numberand type of the source chains, and the like. In certain implementations,processing system 300 maintains a performance history (not shown), anddynamically modifies the processing threshold M based on pastperformance. According to one implementation, M is stochastically set toten (10) seconds. Accordingly, render engine 222 maintains only thechains currently required to support the next ten seconds of execution.It is important to note that project execution does not necessarilycorrelate to rendering of the composite generated by the filter graph.That is, in certain implementations, execution of the filter graph isperformed as fast as possible, utilizing the shared memory resources ofthe matrix switch filter 308 to buffer the composite until the renderingchain consumes the composite.

In block 4204, render engine 222 determines whether a threshold ofloaded chains (e.g., a maximum chain-count) (T) has been exceeded. Incertain implementations, the number of loaded chains will be limited dueto memory limitations. According to one example implementation, settingT equal to one (1) is popular in that it requires the render engine toanalyze the filter graph for chains that are no longer required (e.g.,exhausted chains) whenever a new chain is considered for loading.According to one example implementation, the maximum number of loadedchains supported by render engine 222 is seventy (70). Accordingly, oncerender engine 222 has identified the chains required (block 4202), adetermination is made of whether there is space in which to load theminto the filter graph (block 4204).

If the chain count threshold (T) has not yet been reached, render engine222 loads the identified chains, block 4206. Matrix switch filter 308will initiate execution of the newly loaded chains to fulfill theexecution requirements of the development project.

If, in block 4204 the chain-count threshold (T) has been reached, renderengine 222 determines whether one or more chains may be unloaded fromthe filter graph. Thus, in block 4206, render engine 222 identifies anycurrently loaded chains that will not be utilized in the next N seconds.Source chains may be accessed multiple times to process multipleportions of an associated source. Thus, in accordance with steps4202-4206, a source chain may have been loaded to meet an impendingexecution requirement, and remains loaded to satisfy a subsequentprocessing task. However, where resources are running short, renderengine 222 along with matrix switch filter(s) 308 determine which chainsare not required in the next N seconds and, in block 4210, instructsrender engine 222 to unload the identified chains. As above, N may wellbe dynamically derived based on past performance. In accordance with oneexample implementation, N is thirty (30) seconds. According to oneimplementation, render engine 222 determines whether the chains will berequired for subsequent processing in the current or a future filtergraph. If so, the filter chain is removed from the active filter graphby render engine 222 and cached for subsequent re-integration in this ora future filter graph.

In block 4212, render engine 222 determines whether unloading of theidentified chain(s) in block 4210 has brought the total chain-countbelow the threshold a cutoff threshold (V). According to oneimplementation, V is greater than T. This is particularly useful if Thas been set to one (1), as described above. If so, processing continueswith block 4206 as render engine 222 loads the chains identified inblock 4202.

If, in block 4212, the chain-count threshold is still exceeded, renderengine 222 re-analyzes the current filter graph and identifies thelowest priority chains, block 4214. That is, the filter graph may wellbe comprised of seventy chains, all of which will be required in thenext thirty (N) seconds. If, however, the chains identified in block4202 are needed prior to any of the seventy chains currently loaded inthe filter graph, those chains are assigned a lower priority. Processingcontinues with block 4210 as the lower priority chains are unloaded, asrender engine 222 re-analyzes the chain-count, in block 4212. If thefilter graph has space available, processing continues with block 4206,else it continues with block 4214.

FIG. 43 graphically illustrates an example data structure utilized tomanage dynamic graph building, according to one example implementation.In accordance with the illustrated example embodiment of FIG. 43, afilter graph 4300 is presented. Unlike conventional filter graphimplementations, wherein all chains 4302-4308 would be loaded prior toexecution of the development project, filter graph 4300 illustrates thedynamic nature of the present invention. In the illustrated example ofFIG. 43, matrix switch filter 308 has identified at least two sourcechains 4302, 4304 which are required in the next M seconds to supportthe timely processing of the development project. Such chains areillustrated in FIG. 43 with a solid black line to denote that thesechains are currently loaded into the filter graph 4300. In accordancewith one aspect of the present invention, the development project maywell contain additional chains (e.g., 4306 and 4308) that will berequired to complete execution of the development project, but which arenot yet required and are, thus, not yet loaded. Such chains areillustrated in FIG. 43 with dotted lines, denoting that they are notcurrently loaded into the filter graph 4300. By limiting the number ofcurrently loaded chains to a threshold (T) or, alternatively (V), thepresent implementation reduces the memory requirements necessary tosatisfy even the most complex of development projects by unloadingchains when they are no longer required, without stifling the user'screativity by artificially limiting the size of the filter graph.

FIG. 44 is an example filter graph denoting chain dependencies. Inaccordance with the illustrated example of FIG. 44, filter graph 4400depicts two chains 4402 and 4404, each coupled to an associated matrixswitch filter through an innovative parser object described more fullyin a co-pending patent application entitled A System and Related Methodsfor Reducing the Instances of Source Files in a Filter Graph, filed onDec. 6, 2000 by the inventors of the present application, the disclosureof which is hereby incorporated by reference.

Filter graph 4400 is representative of the situation wherein the sourceis a multimedia file containing both audio and video content, eachrequiring a dedicated pre-processing chain and a matrix switch 308. Itis to be appreciated that in such a situation, where the video chain4202 and the audio chain 4204 share a single instance of a sourcefilter, a dependent relationship with respect to unloading the sourcefilter chain. In such a circumstance, it might not be desirable for thevideo matrix switch, for example, to unload chain 4202 upon completionif, for example, the audio matrix switch requires additional contentfrom the source. Thus, a conventional approach to such a situation wouldbe to invoke separate processing chains, one for the audio content andone for the video content, each having a unique instance of the sourcefilter. The conventional approach has the disadvantage of wasting memoryby invoking multiple instances of the same source. To alleviate thisproblem, the render engine 222 identifies such dependencies within thechain execution list and will not seek to unload the source filter untilboth processing chains no longer require content from the source (e.g.,for at least the next N seconds, as introduced above). In this regard,the present invention alleviates the need to construct two completechains accessing a common source, thereby reducing the memoryrequirements necessary to support more complex processing projects.

Although the invention has been described in language specific tostructural features and/or methodological steps, it is to be understoodthat the invention defined in the appended claims is not necessarilylimited to the specific features or steps described. Rather, thespecific features and steps are disclosed as preferred forms ofimplementing the claimed invention.

1. A method comprising: building an execution list to facilitateprocessing of media content for a user-defined development project, theexecution list comprising: a chain identifier field for holdingidentifiers for identifying chains of components that are to be employedin connection with the development project; a source identifier fieldfor denoting a project source associated with a particular chainidentifier; a project time field for denoting when, during projectexecution, an associated source chain is required; a source time fieldfor denoting which portion of a source is required to support executionof the project for an associated entry in the project time field; and adependencies field for denoting whether an associated chain is dependenton any other chain(s); and using the execution list to organize andexecute the development project, wherein the using comprises dynamicallymanaging, with a matrix switch filter within a filter graph, chainpriorities based, at least in part, on how soon a chain is required tosupport uninterrupted execution of the project.
 2. The method of claim1, wherein the using further comprises determining whether to unload achain prior to its execution.
 3. The method of claim 1, wherein theusing further comprises determining whether to unload a chain or anyassociated dependent chains prior to the chain's execution.
 4. Themethod of claim 1, wherein the using further comprises invoking onlythose chains that are associated with sources that are necessary tosupport a current or impending execution of the filter graph.
 5. Themethod of claim 1, wherein the using further comprises limiting a numberof currently loaded chains to a threshold.
 6. The method of claim 1,wherein the using further comprises unloading a chain when the chain isno longer required.
 7. The method of claim 1, wherein a project sourcecan comprise audio and video content.
 8. The method of claim 1, whereinthe source identifier field can identify a source by using a file name.9. The method of claim 1, wherein the source identifier field canidentify a source by using a file handle.
 10. One or morecomputer-readable media having computer readable instructions thereonwhich implement an execution list to facilitate processing of mediacontent for a user-defined development project, the execution listcomprising: a chain identifier field for holding identifiers foridentifying chains of components that are to be employed in connectionwith the development project; a source identifier field for denoting aproject source associated with a particular chain identifier; a projecttime field for denoting when, during project execution, an associatedsource chain is required; a source time field for denoting which portionof a source is required to support execution of the project for anassociated entry in the project time field; and a dependencies field fordenoting whether an associated chain is dependent on any otherchain(s)/using execution list to organize and execute the developmentproject, wherein the execution list is configured to enable dynamicmanagement, by a matrix switch filter within a filter graph, of chainpriorities based at least in part on how soon a chain is required tosupport uninterrupted execution of the project.
 11. The one or morecomputer-readable media of claim 10, wherein the execution list isfurther configured to enable a determination of whether to unload achain prior to its execution.
 12. The one or more computer-readablemedia of claim 10, wherein the execution list is further configured toenable a determination of whether to unload a chain or any associateddependent chains prior to the chain's execution.
 13. The one or morecomputer-readable media of claim 10, wherein the execution list isfurther configured to enable invocation of only those chains that areassociated with sources that are necessary to support a current orimpending execution of the filter graph.
 14. The one or morecomputer-readable media of claim 10, wherein the execution list isfurther configured to enable limiting a number of currently loadedchains to a threshold.
 15. The one or more computer-readable media ofclaim 10, wherein the execution list is further configured to enableunloading a chain when the chain is no longer required.
 16. The one ormore computer-readable media of claim 10, wherein a project source cancomprise audio and video content.